1. Field of the Invention
The present invention relates to communications systems and, more specifically, to a FM ratio detector.
2. Description of the Prior Art
In communication systems that employ frequency modulation (FM), an information signal is modulated onto a carrier wave to generate an FM signal having a frequency that varies about a carrier frequency. To demodulate an FM signal, a receiver must remove the carrier signal from the received signal, thereby leaving the information signal. To do this, the receiver must be able to determine the carrier frequency of the received signal. However, because of various transmission effects, a received FM signal may exhibit a carrier frequency that deviates from an ideal carrier frequency. Therefore, FM receivers employ a circuit that detects deviation between the received carrier signal and the expected carrier signal and that makes corresponding adjustments to the operating parameters of the demodulation circuit.
Existing digital implementations of frequency deviation (error) detectors lack the speed and precision required for certain applications of communications systems employing intermediate frequency (IF) signals. Therefore, there is a need for an FM ratio detector that has sufficient speed and precision for use in IF communications.